The present invention relates to a radioactive electron emitting microchannel plate. More particularly, to a radioactive electron emitting microchannel plate comprising (a) a pair of parallel substrates; (b) at least one radioactive material layer deposited on an inner surface of the substrates; and (c) at least one electron ray-amplifying layer deposited on the surface of the radioactive material layer.
Electron rays, in general, are generated under electrically stringent conditions. To generate the electron ray from surfaces of metals and semiconductors, a high power electric field of 5 kV/xcexcm or higher should be applied under vacuum. Also, negatively charged electrons should be concentrated in a limited spot to easily emit an electron ray. Such an electron ray-emitting device is referred to as an electron gun.
Difficulties of electron ray emission impose many restrictions on their use in industrial applications. For example, optical lithographic methods are usually used in manufacturing of an integrated circuit pattern. However, they are limited in their resolution by the wavelength of light. Electron ray lithography can provide better resolution than optical lithography, since it doesn""t have the wavelength limitations of optical lithography. However Electron ray couldn""t provide uniform projections on a large area of a wafer in sufficient radiation dose through a single irradiation. Hence, Electron ray have been limited to the fabrication of masks for light projection. In other cases, an image display device, such as a field emission display stimulates a fluorescent material using an electron ray to display an image. In order to generate the electron ray over the whole area of the image display device, many fine cathodic pins are arrayed on the plane. Accordingly, field emission display suffers from complicated structures, difficult fabrication, and shortened lifetimes due to abraded fine negative pins.
To overcome difficulties of artificial electron ray emission, an electron ray-emitting device using a radioactive material generating high-energy radiation is disclosed in U.S. Pat. Nos. 6,215,243 and 4,194,123. In these patents, high-energy radiations, such as alpha rays, beta rays, gamma rays, X-rays, and neutron beams, stimulate the electron ray-amplifying material and thus readily generate the electron ray. The electron ray-generating device using the radioactive material is advantageous in light of its simple flat type construction, in contrast to the complicated structure including the electron gun, but is still disadvantageous in terms of the low radiation dose. Therefore, sufficient amplification of the electron ray is required for application to various apparatuses.
In U.S. Pat. Nos. 6,046,714 and 4,194,123, a microchannel plate, which is an electron ray-amplifying device, is employed. In the microchannel plate, the electron ray passing through the inside of the capillary tube is amplified when reflected onto a wall face of an electron ray amplifying layer deposited on an inner surface of a glass capillary tube. The general microchannel plate structure comprises a bundle of glass capillary tubes, each having a diameter of 5-10 xcexcm, formed in a flat plate being 3-5 cm thick. The microchannel plate has an amplification ratio to 103, and two or three stacked microchannel plates have an amplification ratio of up to 107.
In other methods for amplifying electron rays, U.S. Pat. No. 6,215,243 discloses a method for amplifying electron rays, in which the emitted electron ray is amplified while penetrating through alternately laminated insulating membrane and electron ray amplifying film, in a combination structure of a radiation emitting layer and an electron ray amplifying layer. This electron ray amplification method, however, has a disadvantage in that it is difficult to obtain a sufficient radiation dose. In the case of using the microchannel plate, large dosages of radiation are not introduced into the microchannel plate due to positioning of the radioactive material layer toward an exterior of the plate. As such, the amplified radiation dose is not sufficient. As for such a method, the thickly laminated amplification layer is required to sufficiently amplify the radiation dose. Though a secondary electron ray generated by radiation should be accelerated under high voltage and then further amplified, acceleration is not easily carried out in the solid inside and the energy is drastically decreased. Therefore, disclosed in conventional methods have still many problem so as to efficiently amplify the electron ray.
Leading to the present invention, the intensive and thorough research into a microchannel plate, carried out by the present inventors aiming to avoid the problems encountered in the prior arts, resulted in the finding that an electron ray-emitting microchannel plate comprising (a) a pair of parallel substrates; (b) at least one radioactive material layer deposited on an inner surface of the substrates; and (c) at least one electron ray-amplifying layer deposited on the surface of the radioactive material layer, whereby radioactive material layer is simultaneously combined with electron ray-amplifying layer within the microchannel plate and thus the generated electron ray is amplified by penetrating into the cavity formed by a pair of parallel substrates and is further amplified by reflecting from the electron ray-amplifying layer. Therefore, the microchannel plate emits a sufficient dose of electron ray and easily yields a high-energy beam.
Accordingly, it is an object of the present invention to provide an electron ray emitting a microchannel plate, in accordance with the first embodiment of the present invention, comprising (a) a pair of parallel substrates; (b) at least one radioactive material layer deposited on an inner surface of the substrates; and (c) at least one electron ray-amplifying layer deposited on the surface of the radioactive material layer.
It is another object of the present invention to provide an image display device, in which a cathode and a transparent electrode coated with fluorescent material layer are both positioned at the ends both of the top and the bottom of the capillary tube in the microchannel plate, respectively.
It is further object of the present invention to provide a microchannel plate, which is composed of a stack of thin plates, in accordance with the second embodiment of the present invention, comprising (a) a pair of parallel substrates; (b) at least one radioactive material layer deposited on an inner surface of the substrates; and (c) at least one electron ray-amplifying layer deposited on the surface of the radioactive material layer, wherein the substrate is a thin plate.
It is a further still object of the present invention to provide an electron ray etching device consisting of the microchannel plate suggested in this invention, wherein the electron ray etching device is further comprising an electromagnet focusing lens, a mask, an electron ray sensitive material film, and an electron ray inducing magnet.